1. Field of the Invention
The present invention relates to an ink jet recording head used for a recording apparatus in which recording liquid (e.g., ink) is discharged from a discharge opening to form ink droplets for a recording operation.
2. Description of the Related Art
A general ink jet recording cartridge will be described with reference to FIG. 10. The following section will exemplarily describe a color cartridge from which yellow, magenta, and cyan inks are discharged for a printing operation.
In FIG. 10, an ink jet recording cartridge 601 is structured by integrating an ink jet recording head section including a recording element substrate 702 made of silicon for example and an ink container section 709 including therein ink. The recording element substrate 702 is a heater for allowing ink to be discharged by conversion of electrical energy to thermal energy. The recording element substrate 702 is composed by a nozzle plate that includes: a substrate including a wiring for transmitting electrical energy supplied from an ink jet recording apparatus to the heater; a flow path for supplying ink to the heater; and a plurality of ink discharge openings for discharging ink. One recording element substrate 702 includes discharge opening rows 703, 704, and 705 for discharging ink of three colors of yellow, magenta, and cyan. The electric wiring substrate 706 functions to transmit an electric signal from the ink jet recording apparatus to the recording element substrate 702 by transmitting an electric signal from the ink jet recording apparatus to the recording element substrate 702 via an external signal input terminal 707. The electric wiring substrate 706 is electrically connected to the recording element substrate 702 at two end faces of the recording element substrate 702 so that the electric connection section is covered by sealant 708 for protection from ink.
Next, the general structure of the periphery of the recording element substrate 702 in the ink jet recording head section will be described with reference to FIG. 11 and FIG. 12.
FIG. 11 is a plan view illustrating a support substrate 802 and a support plate 804. The support substrate 802 is made of material such as alumina in order to accurately adhere and fix the recording element substrate 702 and is subjected to a polishing processing. The support plate 804 fixes and supports the electric wiring substrate 706 and is made of the same material as that of the support substrate 802.
FIG. 12 is a cross-sectional view taken along a line XII-XII of FIG. 10. The support substrate 802 includes an ink supply opening 803 for supplying ink in an ink container to the recording element substrate 702. The recording element substrate 702 is attached so that the ink supply opening 803 communicates with the ink supply opening of the recording element substrate 702. A support plate 804 is also attached in order to support the recording element substrate 702. A space between the recording element substrate 702 and the support plate 804 is sealed by sealant 805 (e.g., resin) in order to prevent ink from entering the space. The purpose of this sealing is to prevent, when ink enters the space between the recording element substrate 702 and the support plate 804 and is attached to an end of a side face of the recording element substrate 702, silicon exposed at the end of the side face of the recording element substrate 702 from being eluted and to protect the electric connection section from ink. This sealant 805 is generally thermosetting resin that can be used in a manufacture step in a relatively easy manner.
An accuracy at which the recording element substrate 702 is attached has a direct influence on a recording accuracy of the ink jet recording apparatus. To improve the attachment accuracy or to realize a manufacture step having a high yield, various suggestions have been conventionally made. Japanese Patent Laid-Open No. H10-44420 has proposed that a recording element substrate is fixed by adhering a support substrate having substantially the same thermal characteristic as that of the recording element substrate is adhered to the recording element substrate. Japanese Patent Laid-Open No. 2002-19119 has proposed a method for preventing a recording element substrate from being broken due to different line coefficients of expansion, by adhering a support substrate made of alumina for example between the recording element substrate and the support member.
Cost for a recording element substrate is the highest cost among manufacturing costs for an ink jet recording head. In order to reduce the cost for the recording element substrate, a demand has been recently raised to minimize the size of the recording element substrate so that more recording element substrates can be obtained from one wafer. However, when the substrate size is reduced while leaving the discharge opening arrangement unchanged, a wall section around the discharge opening is reduced, resulting in a wall section having a poor rigidity in the recording element substrate. Since the periphery of the recording element substrate is sealed by the thermosetting resin as described above, the thermosetting resin generates therein, when the thermosetting resin cures and shrinks, a stress that is applied to the recording element substrate. The following section will describe the outline of the stress that is caused when the sealant cures and shrinks and that is applied to the recording element substrate.
FIG. 13 illustrates the stress in the sealant 805 applied to the recording element substrate 702. When a recording head is manufactured, the recording element substrate 702, the support plate 804, and the support substrate 802 and adhesive agent and sealant for fixing them are placed in an oven heated at 100 degrees. Then, the respective members expand by heat and cure while expanding. The respective members have different expansion rates depending on the materials thereof. When the respective cured members are taken out from the oven, the temperatures of the respective members decline to a room temperature and thus the shapes of the expanded members return to the original shapes. It is known that general thermosetting sealant cures and shrinks by about 5%. Thus, stresses shown by arrows in FIG. 13 are caused in the sealant 805 due to the curing and shrinkage of the respective members and the changes with a temperature of the respective members. The opposite side face of the recording element substrate 702 is also in the same condition, although FIG. 13 illustrates only a part of the ink jet recording head and thus does not show the condition of the opposite side face. Specifically, a force from the side face to outside is applied to the recording element substrate 702. When the stress as described above is applied to the recording element substrate 702 as described above, a sectional area at which the recording element substrate 702 has a contact with the sealant 805 is small as shown in FIG. 12 and thus tends to deform when being applied with the stress. Furthermore, the recording element substrate 702 has different opening spaces at a face having a contact with the support substrate 802 and a face opposed to the face. Thus, when the sealant 805 applies a force to the recording element substrate 702, the recording element substrate 702 may deform while having warpage. When a recording head using such a deformed recording element substrate 702 is used for a recording operation, ink droplets discharged from the recording head of an ink jet recording apparatus adhere to a paper in a dislocated manner, thus causing a deteriorated recording quality. Furthermore, the recording element substrate 702 may be broken in a manufacture process.
When the electric wiring substrate 706 and the support plate 804 for supporting the electric wiring substrate 706 from the lower side that respectively have opening sections are adhered by adhesive agent so that the opening sections of the former and the latter are superposed on the other hand, excessive adhesive agent may protrude from an end of the joint face of the joined opening sections. When this protruded adhesive agent moves from the end face of the electric wiring substrate to reach the upper surface, an inconvenience such as a favorable electric joint of the electric joint section or a contact of the electric joint section with a recording medium may be caused. In order to prevent this, the electric wiring substrate 706 has an opening smaller than an opening of the support plate 804. This causes adhesive agent protruding from the end face of the joint section to go down to the interior of the opening section of the support plate 804, thus preventing the adhesive agent from reaching the upper surface of the electric wiring substrate 706.
Another requirement has been made according to which a needle for coating adhesive agent desirably does not have a small inner diameter from the viewpoint of a manufacture efficiency. The present invention has been made in view of the above problems. It is an objective of the present invention to provide an ink jet recording head by which a recording operation having a high recording quality can be stably performed without causing deformation or breakage of the recording element substrate 702 and the manufacture cost is low.